Reinforced concrete and steel bridges are commonly used in the United States; they are strong and relatively lightweight. However, the materials used in these bridges degrade relatively rapidly when subjected to the elements. Steel bridge structures are subject to rusting and corrosion. Reinforced concrete bridge structures are subjected to crumbling and corrosion.
The need to use salt to keep bridge decks clear of ice and/or snow, in addition to causing deterioration of the bridge, also pollutes the runoff from the bridge with the salt and, with many bodies of water, adversely affects the chemical composition of the water and the life cycle of organisms in the water.
Another substantial problem with prior art bridges is that their structural parts, which are often made out of galvanized steel, are attacked and degraded by the chemical pollutants present in automotive emissions and/or in acid rain. Such emissions frequently contains nitrogen oxides and sulfur dioxides, each of which, when they combine with water, form strong acids and cause corrosion.
Covered bridges, such as wooden covered bridges, are well known. However, the prior art covered bridges either did not have the strength and durability of modern day bridges, or were to heavy, or did not adequately resistant to the effects of weathering and chemical attack.
It is an object of this invention to provide a covered bridge structure which is relatively strong, which is relatively lightweight, and which will be substantially more durable than the prior art bridge structures. It is a further object of this invention to provide a covered bridge structure whose structural members are not readily attacked by the pollutants in automotive emissions or in acid rain.